Escherichia coli K12 is unable to grow on any of the four polyhydric pentitols: D-arabitol, L-arabitol, ribitol and xylitol. It has also been unsuccessful to obtain a directmutant of the wild type E. coli to grow on these alcohols. However, after first selecting a mutant for growth on D, L-1, 2-propanediol, we have succeeded in isolating a second-stage mutant which can utilize D-arabitol as the sole source of carbon and energy. Comparing to its parent, the D, L-1, 2-propanediol growing mutant, this second-stage mutant constitutively synthesizes a new dehydrogenase whose native substrate appears as D-galactose. This enzyme also dehydrogenates D-arabitol, and its structural gene is located around 69 minutes of the E. coli genetic map.